Radio device, radio device calibration system, calibration method, and calibration program

ABSTRACT

An adaptive array radio apparatus ( 1010 ) includes an A/D converter ( 1200.1–1200.   n ) receiving respective signals from an array antenna for conversion into a digital signal from an analog signal, a down sampling device ( 1210.1–1210.   n ) receiving an output from the A/D converter ( 1200.1–1200.   n ) for down-sampling, and an adaptive array processing unit ( 1250 ) receiving an output from a synchronizing position estimation device ( 1230 ) to carry out adaptive array processing. In accordance with a timing adjust signal for the down sampling device ( 1210.1–1210.   n ), the minimum square error signal is output from the adaptive array processing unit ( 1250 ). Accordingly, calibration processing having transmission directivity of an adaptive array radio device can be carried out properly.

TECHNICAL FIELD

The present invention relates to a radio apparatus that carries outadaptive array processing, a calibration system, a calibration method oftransmission directivity of a radio apparatus, and a calibration programof transmission directivity.

BACKGROUND ART

In the field of mobile communication systems (for example, PersonalHandyphone System: PHS) evolving rapidly these few years, a PDMA (PathDivision Multiple Access) system that allows radio mobile terminaldevices (hereinafter, terminal) of a plurality of users to effectspatial multiple access to a radio base system (hereinafter, basestation) by dividing the same time slot of the same frequency spatiallyhas been proposed in order to improve the usage efficiency of radiofrequency.

In this PDMA system, the adaptive array technique is employed. Adaptivearray processing is directed to extract a signal properly from a desiredterminal by calculating a weight vector composed of receptioncoefficients (weight) for respective antennas of the base station foradaptive control, based on a reception signal from a terminal.

By such adaptive array processing, the uplink signal from the antenna ofeach user terminal is received by the array antenna of the base station,and then separated and extracted with reception directivity by thereception weights of the current user terminal.

Since there is no variation in the propagation path (the zone betweenthe antenna end of the base station and the antenna end of the terminal)assuming that the time difference between reception and transmission atthe base station is 0, the downlink signal from the base station to therelevant terminal is transmitted from the array antenna of the basestation with transmission directivity towards the antenna of therelevant terminal by applying the reception weights obtained at the timeof receptions as transmission weight information.

The adaptive array processing set forth above is well known in the fieldof art, and described in detail in, for example, “Adaptive SignalProcessing by Array Antenna” (Kagaku Gijutsu Shuppan), issued Nov. 25,1998, pp. 35–49, “Chapter 3: MMSE Adaptive Array” by Nobuyoshi Kikuma.The operating mechanism thereof will be described briefly hereinafter.

In the following description, the base station that provides downlinktransmission directivity control with respect to a terminal employingsuch adaptive array processing will be referred to as adaptive arraybase station hereinafter.

In the PDMA set forth above, the signal of each user is separated usinga frequency filter, time synchronization between the base station andeach user mobile terminal device, and a mutual interference cancellersuch as an adaptive array.

FIG. 8 is a schematic block diagram showing a configuration of atransmission and reception system 2000 of a conventional base stationfor PDMA, realized using an adaptive array radio device.

In the configuration shown in FIG. 8, four antennas #1–#4 are providedto establish identification between a user PS1 and a user PS2.

In a reception operation, the outputs of antennas are provided to an RFcircuit 2101 to be amplified by reception amplifiers, and thenfrequency-converted by a local oscillation signal. The converted signalshave the unnecessary frequency signal removed by filters, are subjectedto A/D conversion, and then applied to a digital signal processor 2102as digital signals.

Digital signal processor 2102 includes a channel allocation referencecalculator 2103, a channel allocating apparatus 2104, and an adaptivearray 2100. Channel allocation reference calculator 2103 calculates inadvance whether the signals from two users can be separated by theadaptive array. Based on the calculation result, channel allocatingapparatus 2104 provides channel allocation information including userinformation, selecting frequency and time, to adaptive array 2100.Adaptive array 2100 applies a weighting operation in real time on thesignals from the four antennas #1–#4 based on the channel allocationinformation to separate only the signals of a particular user.

[Configuration of Adaptive Array Antenna]

FIG. 9 is a block diagram showing a configuration of a transmission andreception unit 2100 a corresponding to one user in adaptive array 2100.The example of FIG. 9 has n input ports 2020-1 to 2020-n to extract thesignal of the desired user from input signals including the signals of aplurality of users.

The signals input to respective input ports 2020-1 to 2020-n are appliedvia respective switch circuits 2010-1 to 2010-n to a weight vectorcontrol unit 2011 and respective multipliers 2012-1 to 2012-n.

Weight vector control unit 2011 calculates weight vectors w_(1i)–w_(ni)using input signals, a unique word signal corresponding to the signal ofa particular user stored in advance in memory 2014, and the output of anadder 2013. As used herein, subscript “i” implies that the weight vectoris employed for transmission/reception with the i-th user.

Multipliers 2012-1 to 2012-n multiply the input signals from input ports2020-1 to 2020-n by weight vectors w_(1i)–w_(ni), respectively. Themultiplied result is applied to adder 2013. Adder 2013 adds the outputsignals from multipliers 2012-1 to 2012-n to output the added signals asa reception signal S_(RX)(t). This reception signal S_(RX)(t) is alsoapplied to weight vector control unit 2011.

Transmission and reception unit 2100 a further includes multipliers2015-1 to 2015-n receiving an output signal S_(TX)(t) to be transmittedfrom the adaptive array radio base station to multiply the same byrespective weight vectors w_(1i)–w_(ni) applied from weight vectorcontrol unit 2011 for output. The outputs of multipliers 2015-1 to2015-n are applied to switch circuits 2010-1 to 2010-n , respectively.Specifically, switch circuits 2010-1 to 2010-n provide the signalsapplied from input ports 2020-1 to 2020-n to a signal receiver unit 1Rin a signal receiving mode, and provides the signal from a signaltransmitter unit 1T to input/output ports 2020-1 to 2020-n in a signaltransmission mode.

[Operating Mechanism of Adaptive Array]

The operating mechanism of transmission and reception unit 2100 a ofFIG. 9 will be described briefly here.

For the sake of simplfying the description hereinafter, it is assumedthat there are four antenna elements, and two users PS effectcommunication at the same time. In such a case, signals applied toreception unit 1R from respective antennas are represented by theequations set forth below.RX ₁(t)=h ₁₁ Srx ₁(t)+h ₁₂ Srx ₂(t)+n ₁(t)  (1)RX ₂(t)=h ₂₁ Srx ₁(t)+h ₂₂ Srx ₂(t)+n ₂(t)  (2)RX ₃(t)=h ₃₁ Srx ₁(t)+h ₃₂ Srx ₂(t)+n ₃(t)  (3)RX ₄(t)=h ₄₁ Srx ₁(t)+h ₄₂ Srx ₂(t)+n ₄(t)  (4)

Signal RX_(j)(t) represents a reception signal of the j-th (j=1, 2, 3,4) antenna. Signal Srx_(i)(t) represents a signal transmitted by thei-th (i=1, 2) user.

Coefficient h_(ji) represents the complex coefficient of a signal fromthe i-th user received at the j-th antenna, and n_(j)(t) represents thenoise included in the j-th reception signal.

The above equations (1)–(4) may be represented in vector form asfollows:X(t)=H ₁ Srx ₁(t)+H ₂ Srx ₂(t)+N(t)  (5)X(t)=[RX ₁(t), RX ₂(t), . . . RX ₄(t)]^(T)  (6)H _(i) =[h _(1i) , h _(2i) , . . . , h _(4i)]^(T), (i=1, 2)  (7)N(t)=[n ₁(t), n ₂(t), . . . n ₄(t)]^(T)  (8)

In equations (6)–(8), [ ] T denotes the transposition of [. . . ]. Here,X (t) represents the input signal vector, H_(i) the reception signalcoefficient vector of the i-th user, and N (t) a noise vector.

The adaptive array antenna outputs as a reception signal S_(RX)(t) asynthesized signal obtained by multiplying the input signals fromrespective antennas by respective weight coefficients w_(1i)–w_(ni), asshown in FIG. 9.

Given these preliminaries, the operation of an adaptive array in thecase of extracting a signal Srx₁(t) transmitted by, for example, thefirst user is set forth below.

Output signal y1 (t) of adaptive array 2100 can be represented by thefollowing equations by multiplying input signal vector X(t) by weightvector W₁.y1(t)=X(t)W ₁ ^(T)  (9)W ₁ =[W ₁₁ , W ₂₁ , W ₃₁ , W ₄₁]^(T)  (10)In other words, weight vector W₁ is a vector with the weightcoefficients w_(j1) (j=1, 2, 3, 4) to be multiplied by the j-th inputsignals RXj (t) as elements.

Substituting input signal vector X (t) represented by equation (5) intoy1(t) represented by equation (9) yields:y1(t)=H ₁ W ₁ ^(T) Srx ₁(t)+H ₂ W ₁ ^(T) Srx ₂(t)+N(t)W ₁ ^(T)  (11)

By a well known method, weight vector W₁ is sequentially controlled byweight vector control unit 2011 so as to satisfy the followingsimultaneous equations when adaptive array 2100 operates in an idealsituation. As used herein, the adaptive array processing to obtain suchweight vectors determines the optimum weight by minimizing thedifference (error signal) between the reference signal that is thedesired array response and the actual array output signal. In thisminimization of the error signal, the minimum mean square error (MMSE)method is employed.H ₁ W ₁ ^(T)=1  (12)H ₂ W ₁ ^(T)=0  (13)

If weight vector W₁ is perfectly controlled so as to satisfy equations(12) and (13), output signal y1(t) from adaptive array 2100 iseventually represented by the following equations.y 1(t)=Srx ₁(t)+N ₁(t)  (14)N ₁(t)=n ₁(t)w ₁₁ +n ₂(t)W ₂₁ +n ₃(t)W ₃₁ +n ₄(t)W ₄₁  (15)

Specifically, signal Srx₁(t) emitted from the first of the two userswill be obtained for output signal y1(t).

In FIG. 9, input signal S_(TX)(t) for adaptive array 2100 is applied totransmitter unit 1T in adaptive array 2100 to be applied to respectiveone inputs of multipliers 2015-1, 2015-2, 2015-3, . . . , 2015-n. To theother inputs of these multipliers, weight vectors w_(1i), w_(2i),w_(3i), . . . , w_(ni) calculated by weight vector control unit 2011based on reception signals described above are copied and applied.

The input signals weighted by these multipliers are delivered tocorresponding antennas #1, #2, #3, . . . , #n via corresponding switches2010-1, 2010-2, 2010-3, 2010-n for transmission.

Identification of users PS1 and PS2 is made as set forth below. A radiowave signal of a cellular phone is transmitted in frame form. The radiowave signal of a cellular phone is mainly composed of a preamble formedof a signal series known to a radio base station, and data (voice andthe like) formed of a signal series unknown to the radio base station.

The preamble signal series includes a signal stream of information toidentify whether the current user is the appropriate user to conversefor the radio base station. Weight vector control unit 2011 of adaptivearray radio base station 1 compares the unique word signal correspondingto user A output from memory 2014 with the received signal series toconduct weight vector control (determine weight coefficients) so as toextract the signal expected to include the signal series correspondingto user PS1.

[Calibration of Adaptive Array Radio Device]

However, even if there is no variation in the propagation path,difference in transmission characteristics such as in the phase rotationand amplitude variation between transmission and reception signals willoccur between the reception signal path and the transmission signal pathdue to the physical difference between the reception signal path and thetransmission signal path in the adaptive array base station (forexample, due to the difference in the path length, difference in theproperties of the device such as amplifiers and filters included in thereception circuit and the transmission circuit, and the like).

If there is difference in the transmission characteristics between thetransmission and reception signals within the adaptive array basestation, the optimum transmission directivity cannot be directed to theterminal of the transmission destination based on the method thatdirectly employs the reception weight set forth above as thetransmission weight.

Thus, calibration is generally carried out to compensate for thedifference between the transmission characteristic of the receptionsignal path and the transmission characteristic of the transmissionsignal path within the base station at the time of shipment from thefactory to achieve the optimum transmission directivity.

FIG. 10 is a schematic block diagram to describe the configuration of acalibration system 3000 directed to conducting, at the time of shipmentfrom the factory, calibration with respect to adaptive array basestation 3010 identified as the base station.

Referring to FIG. 10, calibration-system 3000 includes an adaptive arrayradio device 3010 that is the subject of calibration, a clock generator3020 to generate a reference clock for the calibration mode, signalgenerators 3030.1 and 3030.2 generating modulating signals to be usedfor calibration, a spectrum analyzer 3040 to measure the power of asignal transmitted from adaptive array radio device 3010, a powerdivider 3060 arranged between signal generators 3030.1, 3030.2 andadaptive array radio device 3010, a circulator 3050 to selectively passthrough a signal in a direction from a node corresponding to signalgenerator 3030.2 of power divider 3060 towards spectrum analyzer 3040and in a direction from signal generator 3030.2 towards power divider3060, attenuators 3070.1-3070.n provided between the nodes correspondingto the plurality of antennas of adaptive array radio device 3010 and theplurality of input/output nodes of the power divider, and a controlpersonal computer (referred to as “control PC” hereinafter) 3100 tocontrol the calibration operation.

Power divider 3060 may be a Butler matrix.

A conventional calibration operation will be described brieflyhereinafter.

Based on a measurement device control signal from control PC 3100,signal generators 3030.1 and 3030.2 generate modulating signals forcalibration. These modulating signals are applied to adaptive arrayradio device 3010 via power divider 3060 and attenuators 3070.1-3070.n.

At adaptive array radio device 3010, the transmission weight is adjustedso as to have directivity with respect to a signal from signal generator3030.1 in accordance with the radio device control signal from controlPC 3100. If the transmission characteristic of the reception signal pathmatches the transmission characteristic of the transmission signal pathof adaptive array radio device 3010 in this state of affairs, the powerof the signal towards signal generator 3030.2, i.e. the power detectedby spectrum analyzer 3040, should be “0”.

However, in practice, there is deviation in the transmissioncharacteristic of the reception signal path from the transmissioncharacteristic of the transmission signal path in adaptive array radiodevice 3010. Therefore, a correction value must be applied to theamplitude and phase of the transmission weight calculated at adaptivearray radio device 3010 so as to adjust the power detected at spectrumanalyzer 3040 to become “0”.

To this end, the correction values to be applied to the amplitude andphase of the transmission weight calculated at adaptive array radiodevice 3101 are sequentially modified while monitoring the measurementvalue of spectrum analyzer 3040 to find an optimum correction value.

By such a procedure, calibration can be conducted with respect toadaptive array radio device 3010.

However, in the conventional calibration system 3000 set forth above,the reception timing of adaptive array radio device 3010 is insynchronization with the signal output timing of signal generators3030.1 and 3030.2 of the measurement system based on a clock signal froma common clock generator 3020.

If the sampling timing of analog-digital conversion (A/D conversion)carried out during signal processing at adaptive array radio device 3010is an integral multiple of or is 1/integer times the external clock insuch a system, the timing between the measurement system and adaptivearray radio device 3010 can be made to match without any error. Inpractice, the sampling timing of A/D conversion is not an integralmultiple of or 1/integer times the external clock. Therefore, there issome error between the timings thereof. Thus, there was a problem thatthere is an error in the calibration correction value.

It is to be further noted that calibration processing is carried outwith the synchronization of the reception signal fixed, based on theassumption that the apparatus is configured so as to establishsynchronization between the measurement system and adaptive array radiodevice 3010. However, even with such measurement form based on fixation,the occasion arises where there is deviation of approximately severalsymbols in synchronization between adaptive array radio device 3010 andthe measurement system due to aging and the like. There was a problemthat the clock must be adjusted again on such events.

In view of the foregoing, an object of the present invention is toprovide a radio apparatus that can conduct calibration processing oftransmission directivity properly for an adaptive array radio device, acalibration system, a calibration method of transmission directivity,and a calibration program of transmission directivity.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, a radio apparatus thatcarries out signal reception by adaptive array processing includes aplurality of antennas, and signal conversion means sampling signals fromthe plurality of antennas for conversion into a digital signal from ananalog signal. The signal conversion means has a variable timing ofsampling in accordance with a timing adjust signal. The radio apparatusfurther includes adaptive array processing means for calculating, basedon a signal from the signal conversion means, a reception weight toextract a desired signal, and a transmission weight to form a pattern ofdesired transmission directivity. The adaptive array processing meansoutputs match information that provides an indication of the desiredreception directivity being achieved in the calculation of the receptionweight. The radio apparatus further includes a first interface toreceive the timing adjust signal from outside the radio apparatus, and asecond interface to output the match information outside the radioapparatus.

Preferably, the signal conversion means includes A/D conversion meansfor sampling a signal from the plurality of antennas at a firstfrequency, and down sampling means for sampling at a second frequencylower than the first frequency the signal sampled at the firstfrequency. The down sampling means modifies the sampling timing at thesecond frequency in accordance with the timing adjust signal.

Preferably, the down sampling means modifies a sampling timing at thesecond frequency in units of timing intervals corresponding to the firstfrequency in accordance with the timing adjust signal.

Preferably, the signal conversion means includes A/D conversion meansfor sampling a signal from the plurality of antennas at a firstfrequency, and means for adjusting a phase of an internal clock definingthe sampling timing at the first frequency by the A/D conversion meansin accordance with the timing adjust signal.

According to another aspect of the present invention, a calibrationsystem to calibrate a transmission directivity of a radio apparatus thatcarries out signal reception by adaptive array processing using aplurality of antennas includes control means for controlling acalibration operation, and a plurality of signal generation means forgenerating respective plurality of test signals to be applied to theradio apparatus under control of the control means. The radio apparatusincludes signal conversion means sampling a signal from the plurality ofantennas for conversion into a digital signal from an analog signal. Thesignal conversion means has a variable timing of sampling in accordancewith a timing adjust signal. The radio apparatus further includesadaptive array processing means for calculating, based on a signal fromthe signal conversion means, a reception weight to extract a desiredsignal, and a transmission weight to form a pattern of a desiredtransmission directivity. The adaptive array processing means outputsmatch information that provides an indication of the desired receptiondirectivity being achieved in the calculation of a reception weight. Theradio apparatus further includes a first interface for receiving atiming adjust signal from the control means, and a second interface forproviding the match information to the control means. The control meansdetermines a level of the timing adjust signal by which the desiredreception directivity is achieved, based on correspondence between thetiming adjust signal and the match information.

Preferably, the calibration system further includes detection means,provided corresponding to at least one of the plurality of signalgeneration means, for detecting a level of a signal output from theradio apparatus with respect to a corresponding signal generation meansunder control of the control means. The control means determines acorrection value for the transmission weight in accordance with adetected result of the detection means.

Preferably, the signal conversion means includes A/D conversion meansfor sampling a signal from the plurality of antennas at a firstfrequency, and down sampling means for sampling at a second frequencylower than the first frequency the signal sampled at the firstfrequency. The down sampling means modifies a sampling timing at thesecond frequency in accordance with the timing adjust signal.

Preferably, the signal conversion means includes A/D conversion meansfor sampling a signal from the plurality of antennas at the firstfrequency, and means for adjusting a phase of an internal clock definingthe sampling timing at the first frequency by the A/D conversion meansin accordance with the timing adjust signal.

According to a further aspect of the present invention, a calibrationmethod of transmission directivity at a radio apparatus that carries outsignal reception by adaptive array processing using a plurality ofantennas includes the steps of generating respective plurality of testsignals to be applied to the radio apparatus, sampling a signal from theplurality of antennas for conversion into a digital signal from ananalog signal at the radio apparatus, modifying a sampling timing at thesignal conversion step in accordance with a timing adjust signal,calculating a reception weight to extract a desired signal based on asignal-converted signal to output match information that provides anindication of a desired reception directivity being achieved,determining a level of the timing adjust signal by which the desiredreception directivity is achieved based on the correspondingrelationship between the timing adjust signal and the match information,obtained by sequentially modifying a level of the timing adjust signal,calculating a transmission reception weight to form a pattern of adesired transmission directivity at the determined level of a timingadjust signal, detecting a level of the signal output from the radioapparatus corresponding to the transmission weight, and determining thecorrection value for the transmission weight in accordance with adetected result of the signal level.

Preferably, the signal conversion step includes the steps of sampling asignal from the plurality of antennas at a first frequency, sampling ata second frequency lower than the first frequency the signal sampled atthe first frequency, and modifying the a sampling timing at the secondfrequency in accordance with the timing adjust signal.

Preferably, the signal conversion step includes the steps of sampling asignal from the plurality of antennas at a first frequency, andadjusting a phase of an internal clock defining the sampling timing atthe first frequency in accordance with the timing adjust signal.

According to still another aspect of the present invention, acalibration program of transmission directivity at a radio apparatusthat carries out signal reception by adaptive array processing using aplurality of antennas causes a computer to execute the steps ofgenerating respective plurality of test signals to be applied to theradio apparatus, sampling a signal from the plurality of antennas forconversion into a digital signal from an analog signal for the radioapparatus, modifying a sampling timing at the signal conversion step inaccordance with a timing adjust signal for the radio apparatus,calculating a reception weight to extract a desired signal based on asignal-converted signal and outputting match information that providesan indication of a desired reception directivity being achieved withrespect to the radio apparatus, determining a level of the timing adjustsignal by which the desired reception directivity is achieved based onthe corresponding relationship between the timing adjust signal and thematch information, obtained by sequentially modifying the level of thetiming adjust signal, calculating a transmission weight to form apattern of the desired transmission directivity at the determined levelof a timing adjust signal with respect to the radio apparatus, detectinga level of the signal output from the radio apparatus corresponding tothe transmission weight, and determining a correction value for thetransmission weight in accordance with a detected result of the signallevel.

Preferably, the signal conversion step includes the steps of sampling asignal from the plurality of antennas at the first frequency, samplingat a second frequency lower than the first frequency the signal sampledat the first frequency, and modifying a sampling timing at the secondfrequency in accordance with the timing adjust signal.

Preferably, the signal conversion step includes the steps of sampling asignal from the plurality of antennas at a first frequency, andadjusting a phase of an internal clock defining the sampling timing atthe first frequency in accordance with the timing adjust signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram to describe a configuration of acalibration system 1000 of the present invention.

FIG. 2 is a block diagram to describe in further detail a configurationof an adaptive array radio device 1010 and a configuration of control PC1100 according to a first embodiment of the present invention.

FIGS. 3A–3C are diagrams representing the sampling timing of respectiveelements in calibration system 1000 according to the first embodiment ofthe present invention.

FIG. 4 is a flow chart to describe an operation of calibration system1000 according to the first embodiment of the present invention.

FIG. 5 is a block diagram to describe in further detail a configurationof an adaptive array radio device 1010 and a configuration of control PC1100 according to a second embodiment of the present invention.

FIGS. 6A–6C are diagrams representing the sampling timing of respectiveelements in calibration system 1000 according to the second embodimentof the present invention.

FIG. 7 is a flow chart to describe an operation of calibration system1000 according to the second embodiment of the present invention.

FIG. 8 is a schematic block diagram representing a configuration of atransmission and reception system 2000 of a conventional PDMA basestation realized using an adaptive array radio device.

FIG. 9 is a block diagram showing a configuration of a transmission andreception unit 2100 a corresponding to one user in adaptive array 2100.

FIG. 10 is a schematic block diagram to describe a configuration of acalibration system 3000.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detailhereinafter with reference to the drawings.

FIG. 1 is a schematic block diagram to describe a configuration of acalibration system 1000 of the present invention for carrying out, atthe time of shipment from the factory, calibration for an adaptive arrayradio device 1010 identified as a base station.

Referring to FIG. 1, a calibration system 1000 includes an adaptivearray radio device 1010 that is the subject of calibration, a clockgenerator 1020 to generate a reference clock for calibration, signalgenerators 1030.1 and 1030.2 generating modulating signals to be usedfor calibration, a spectrum analyzer 1040 to measure the power of asignal transmitted from adaptive array radio device 1010, a powerdivider 1060 arranged between signal generators 1030.1, 1030.2 andadaptive array radio device 1010, a circulator 1050 to selectively passthrough a signal in a direction from a node corresponding to signalgenerator 1030.2 of power divider 1060 towards spectrum analyzer 1040and in a direction from signal generator 1030.2 towards power divider1060, attenuators 1070.1–1070.n arranged between nodes corresponding tothe plurality of antennas of adaptive array radio device 1010 and theplurality of input/output nodes of the power divider, and a control PC1100 to control the calibration operation.

Power divider 1060 may be a Butler matrix.

The control PC is installed with a program to calibrate adaptive arrayradio device 1010 upon implementing the procedure to compensate forsampling timing error in A/D conversion of adaptive array radio device1010.

Additionally, a timing adjuster 1012 to set a variable timing ofsampling in A/D conversion in accordance with the control of the controlPC is provided at adaptive array radio device 1010.

[First Embodiment]

FIG. 2 is a block diagram to describe in further detail a configurationof adaptive array radio device 1010 and a configuration of control PC1100 according to the first embodiment of the present invention.

In the configuration of adaptive array radio device 1010, the elementsin direct relation with calibration, though not illustrated, areprovided in practice as described with reference to FIG. 9.

The signal transmitted between a base station and a terminal is dividedinto a plurality of frames. The signals of 1 frame are divided into 8slots, the 4 slots of the former half directed to, for example,reception, and the 4 slots of the latter half directed to, for example,transmission.

Each slot is formed of 120 symbols. Based on one set of one slot forreception and one slot for transmission, the signal of 1 frame can beallocated to, for example, up to 4 users.

Referring to FIG. 2, adaptive array radio device 1010 includes A/Dconverters 1200.1–1200.n receiving respective signals from antennas#1–#n constituting the array antenna to carry out sampling at a timingdefined by an internal clock supplied from a clock generation device notshown and at a predetermined frequency for conversion into a digitalsignal from an analog signal, down sampling devices 1210.1–1210.nreceiving outputs from A/D converters 1200.1–1200.n to carry out downsampling until a frequency to carry out calculation of adaptive arrayprocessing is achieved. As will be described afterwards, each of downsampling devices 1210.1–1210.n can modify the timing of down sampling inaccordance with a control signal applied from control PC 1100 viainterface 1220. A/D converters 1200.1–1200.n and down sampling devices1210.1–1210.n correspond to timing adjuster 1012.

Adaptive array radio device 1010 further includes a synchronizingposition estimation device 1230 receiving outputs from down samplingdevices 1210.1–1210.n to detect the head position of a reception signalslot, an interface 1240 receiving and applying to synchronizing positionestimation device 1230 a control signal from control PC 1100, anadaptive array processing unit 1250 receiving the output ofsynchronizing position estimation device 1230 to carry out adaptivearray processing, and an interface 1260 applying from control PC 1100 toadaptive array processing unit 1250 a correction value for the amplitudeand phase to be applied to the transmission weight, or applying to thecontrol PC a minimum square error signal (MSE) that provides anindication of a desired directivity being achieved in carrying outadaptive array processing in adaptive array processing unit 1250.

Although only the configuration for receiving a signal is depicted inFIG. 2, adaptive array processing unit 1250 calculates, in practice, atransmission weight to provide a desired transmission directivity basedon the received signal. Based on the transmission weight, a radio wavehaving transmission directivity for a desired terminal is output,likewise FIG. 9, with respect to the transmission signal from adaptivearray radio device 1010. At this stage, the transmission weight issubjected to correction based on the correction value set forth above.

Control PC 1100 includes a central processing unit (CPU) 1102 carryingout an operation to control the calibration processing that will bedescribed hereinafter in accordance with the control program, and amemory 1104 to store, in addition to the aforementioned control program,the timing adjustment with respect to down sampling devices1210.1–1210.n and the minimum square error signal in association, aswill be described afterwards.

FIGS. 3A–3C represent the sampling timing of respective elements incalibration system 1000 according to the first embodiment of the presentinvention. FIG. 3A represents the sampling timing of A/D converters1200.1–1200.n. FIG. 3B represents the sampling timing of down samplingdevices 1210.1–1210.n. FIG. 3C represents the minimum square errorsignal (MSE) stored in memory 1104 while the timing of down samplingdevices 1210.1–1210.n is adjusted.

As shown in FIG. 3A, the sampling by A/D converters 1200.1–1200.n iscarried out at a frequency higher than the frequency of the sampling bydown sampling devices 1200.1–1200.n of FIG. 3B.

Therefore, if sampling is carried out by down sampling devices1210.1–1210.n at the timing of, for example, FIG. 3B, the minimum squareerror signal values as indicated by the black circle in FIG. 3C areobtained.

By gradually altering the timing of sampling of down sampling devices1210.1–1210.n shown in FIG. 3B in steps of the sampling time interval ofA/D converters 1200.1–1200.n in accordance with the control signals fromcontrol PC 1100, data equivalent to that obtaining the characteristicsas represented by the open circles and hatched circles in FIG. 3C can beeventually obtained.

Therefore, even in the case where the sampling timing of A/D conversionis not based on an integral multiple of or 1/integer times the externalclock, the true synchronizing position can be found. Thus, calibrationis carried out.

FIG. 4 is a flow chart to describe the operation of calibration system1000 according to the first embodiment.

Upon initiation of calibration (step S100), control PC 1100 outputs aninstruction to adaptive array radio device 1010 (base station) to setthe timing of sampling of down sampling devices 1210.1–1210.n to anappropriate initial value. Adaptive array radio device 1010 receivessignals (SG signal) from signal generators 1030.1 and 1030.2 to measurethe minimum square error signal value (MSE), and notifies control PC1100 the measured minimum square error signal value. Control PC 1100stores the value of the timing adjustment and the value of the minimumsquare error signal value in correspondence (step S1012).

Control PC 1100 instructs that the sampling timing of down samplingdevices 1210.1–1210.n in adaptive array radio device 1010 is to bemodified by just one step of the sampling time interval of A/Dconverters 1200.1–1200.n (step S104).

Then, adaptive array radio device 1010 receives the SG signal, measuresthe minimum square error signal value (MSE), and notifies control PC1100 the newly measured minimum square error signal value. Control PC1100 stores the value of the timing adjustment and the value of theminimum square error signal value in correspondence (step S106).

Control PC 1100 determines whether the minimum square error signal valueis equal to or below a predetermined value, and can be identified as theminimum value (step S108).

When not identified as the minimum, an instruction is output to modifythe sampling timing of down sampling devices 1210.1–1210.n in adaptivearray radio device 1010 to an appropriate value, for example, modify thetiming by just one step of the sampling time interval of A/D converters1200.1–1200.n (step S110). Then, the process returns to step S106.

When determination is made that the minimum square error signal value isequal to or below a predetermined value and can be identified as theminimum at control PC 1100, calibration is executed in a manner similarto that of the conventional case with the timing adjust value fixedcorresponding to the minimum (step S112). Thus, the calibrationprocessing ends (step S114).

By the above-described configuration, the calibration processing oftransmission directivity of an adaptive array radio device can becarried out properly.

Second Embodiment

FIG. 5 is a block diagram to describe in further detail a configurationof adaptive array radio device 1010 and control PC 1100 according to asecond embodiment of the present invention.

Referring to FIG. 5, adaptive array radio device 1010 includes A/Dconverters 1201.1–1201.n receiving respective signals from antennas#1–#n constituting the array antenna to carry out sampling at a timingdefined by an internal clock supplied from a clock generation device notshown and at a predetermined frequency directed to carrying out thecalculation of adaptive array processing for conversion into a digitalsignal from an analog signal. Each of A/D converters 1201.1–1201.n canmodify the clock phase that determines the timing of sampling inaccordance with a clock phase adjust signal supplied from a phaseadjuster 1270 based on a control signal applied from control PC 1100 viainterface 1220. A/D converters 1201.1–1201.n and phase adjuster 1270correspond to timing adjuster 1012.

Adaptive array radio device 1010 further includes a synchronizingposition estimation device 1230 receiving outputs from A/D converters1201.1–1201.n to detect the head position of a reception signal slot, aninterface 1240 receiving and applying to synchronizing positionestimation device 1230 a control signal from control PC 1100, anadaptive array processing unit 1250 receiving an output fromsynchronizing position estimation device 1230 to carry out adaptivearray processing, and an interface 1260 applying from control PC 1100 toadaptive array processing unit 1250 a correction value for the amplitudeand phase to be applied to a transmission weight, or applying theminimum square error signal (MSE) that provides an indication of adesired-directivity being achieved to the control PC in carrying outadaptive array processing at adaptive array processing unit 1250.

Although only the configuration for receiving a signal is shown in FIG.5, adaptive array processing unit 1250 calculates, in practice, atransmission weight to provide a desired transmission directivity basedon the received signal. Based on the transmission weight, a radio wavehaving transmission directivity for a desired terminal is output,likewise FIG. 9, with respect to the transmission signal from adaptivearray radio device 1010. At this stage, the transmission weight issubjected to correction based on the correction value set forth above.

Control PC 1100 includes a central processing unit (CPU) 1102 to carryout an operation to control calibration processing set forth below inaccordance with a control program, and a memory 1104 to store, inaddition to the aforementioned control program, the timing adjustmentwith respect to A/D converters 1201.1–1201.n and the minimum squareerror signal in correspondence, as will be described afterwards.

FIGS. 6A–6C represent the sampling timing of respective elements incalibration system 1000 according to the second embodiment of thepresent invention. FIG. 6A represents the sampling timing when phaseadjustment of A/D converters 1201.1–1201.n is not conducted. FIG. 6Brepresents the sampling timing when phase adjustment of A/D converters1201.1–1201.n is conducted. FIG. 6C represents the minimum square errorsignal value (MSE) stored in memory 0.1104 while the clock phaseadjustment of A/D converters 1201.1–1201.n , i.e. sample timingadjustment, is carried out.

In the second embodiment of FIG. 5, down sampling devices such as thosein the first embodiment of FIG. 2 are not provided. A/D converters1201.1–1201.n shown in FIG. 6A have a sampling frequency lower than thesampling frequency of A/D converters 1200.1–1200.n of the firstembodiment of FIG. 3A, as the frequency for calculation of adaptivearray processing.

Therefore, if A/D converters 1201.1–1201.n carry out sampling at the lowfrequency of FIG. 6A, for example, all the data input at a frequency ofhigh speed as shown in FIG. 6C cannot be sampled.

Therefore, in the second embodiment, sampling is carried out over aplurality of times while adjusting the sampling timing (the phase of theinternal clock defining the same). Adaptive array reception is conductedfor each sampling timing, and the minimum square error signal value isrecorded.

In the example of FIG. 6C, the minimum square error signal valuesobtained by sampling at the first sampling timing are represented by thecircle A. The minimum square error signal values obtained by sampling atthe second sampling timing shifted in phase are represented by thecircle B. The minimum square error signal values obtained by sampling atthe third sampling timing further shifted in phase are represented bythe circle C.

By applying the clock adjust signal that defines a sample timingcorresponding to the smallest minimum square error signal value that isrecorded (circle of C) shown in FIG. 6C from phase adjuster 1270 to A/Dconverters 1201.1–1201.n , the sampling timing is adjusted as shown inFIG. 6B.

Therefore, even if the sampling timing of A/D conversion is not anintegral multiple of or 1/integer times the external clock, the truesynchronizing position can be found so that calibration can be carriedout.

FIG. 7 is a flow chart to describe the operation of calibration system1000 according to the second embodiment.

Upon initiation of calibration (step S200), an instruction is outputfrom control PC 1100 to adaptive array radio device 1010 (base station)to set the clock phase adjust value defining the sampling timing of A/Dconverters 1201.1–1201.n to an appropriate initial value. Adaptive arrayradio device 1010 receives signals (SG signals) from signal generators1030.1 and 1030.2 to measure the minimum square error signal value(MSE), and notifies control PC 1100 the measured minimum square errorsignal value. Control PC 1100 stores the value of clock phase adjustmentand the value of the minimum square error signal value signal incorrespondence (step S202).

Control PC 1100 instructs phase adjuster 1270 in adaptive array radiodevice 1010 to modify the phase of the internal clock that defines thesampling timing of A/D converters 1201.1–1201.n by just 1 stepcorresponding to 1/integer times the time interval of sampling of A/Dconverters 1201.1–1201.n (step S204).

Then, adaptive array radio device 1010 receives a SG signal, measuresthe minimum square error signal value (MSE), and notifies control PC1100 the newly measured minimum square error signal value. Control PC1100 stores the value of clock phase adjustment and the value of theminimum square error signal value in correspondence (step S206).

Then, control PC 1100 determines whether the minimum square error signalvalue is equal to or below a predetermined value, and can be identifiedas the minimum value (step S208).

When not identified as the minimum, an instruction is output to furthermodify the sampling timing of A/D converters 1201.1–1201.n with respectto phase adjuster 1270 in adaptive array radio device 1010 by just onestep corresponding to 1/integer times the time interval of sampling ofA/D converters 1201.1–1201.n to an appropriate value (step S210). Then,the process returns to step S206.

When determination is made that the minimum square error signal value isequal to or below a predetermined value and can be identified as themaximum at control PC 1100, calibration is executed in a manner similarto that of the conventional case with the clock adjust value fixedcorresponding to the minimum (step S212). Thus, the calibration processends (step S214).

By the above-described configuration, calibration processing oftransmission directivity of an adaptive array radio device can becarried out properly.

In the present invention, calibration processing of transmissiondirectivity of an adaptive array radio device can be carried outproperly even in the case where the sampling timing of A/D conversion inthe adaptive array radio device is not an integral multiple of or1/integer times the external clock.

Further, calibration processing of transmission directivity of anadaptive array radio device can be carried out properly even in the casewhere there is synchronization shift of several symbols between theadaptive array radio device and the measurement system due to aging andthe like.

INDUSTRIAL APPLICABILITY

In accordance with the present invention, deviation in clock frequencybetween the adaptive array radio device and the measurement system canbe adjusted, effective for calibration of transmission directivity of anadaptive array radio device.

1. A radio apparatus carrying out signal reception by adaptive arrayprocessing, comprising: a plurality of antennas, signal conversion meanssampling a signal from said plurality of antennas for conversion into adigital signal from an analog signal, said signal conversion meanshaving a variable timing of sampling in accordance with a timing adjustsignal, and adaptive array processing means for calculating, based on asignal from said signal conversion means, a reception weight to extracta desired signal, and a transmission weight to form a pattern of adesired transmission directivity, wherein said adaptive array processingmeans outputs match information that provides an indication of thedesired reception directivity being achieved in calculation of saidreception weight, further comprising: a first interface for receivingsaid timing adjust signal from outside said radio apparatus, and asecond interface to output said match information outside said radioapparatus.
 2. The radio apparatus according to claim 1, wherein saidsignal conversion means comprises A/D conversion means for sampling asignal from said plurality of antennas at a first frequency, and downsampling means for sampling at a second frequency lower than said firstfrequency said signal sampled at the first frequency, wherein said downsampling means modifies a sampling timing at said second frequency inaccordance with said timing adjust signal.
 3. The radio apparatusaccording to claim 2, wherein said down sampling means modifies asampling timing at said second frequency in units of time intervalscorresponding to said first frequency in accordance with said timingadjust signal.
 4. The radio apparatus according to claim 1, wherein saidsignal conversion means comprises A/D conversion means for sampling asignal from said plurality of antennas at a first frequency, and meansfor adjusting a phase of an internal clock defining the sampling timingat the first frequency by said A/D conversion means in accordance withsaid timing adjust signal.
 5. A calibration system to calibrate atransmission directivity of a radio apparatus that carries out signalreception by adaptive array processing using a plurality of antennas,comprising: control means for controlling a calibration operation, and aplurality of signal generation means for generating respective pluralityof test signals to be applied to said radio apparatus under control ofsaid control means, wherein said radio apparatus comprises signalconversion means sampling a signal from said plurality of antennas forconversion into a digital signal from an analog signal, said signalconversion means having a variable timing of sampling in accordance witha timing adjust signal, adaptive array processing means for calculating,based on a signal from said signal conversion means, a reception weightto extract a desired signal, and a transmission weight to form a patternof a desired transmission directivity said adaptive array processingmeans outputting match information that provides an indication of thedesired reception directivity being achieved in calculation of saidreception weight, and further comprises a first interface for receivingsaid timing adjust signal from said control means, and a secondinterface for providing said match information to said control means,wherein said control means determines a level of said timing adjustsignal by which the desired reception directivity is achieved, based onthe correspondence between said timing adjust signal and said matchinformation.
 6. The calibration system according to claim 5, furthercomprising detection means, provided corresponding to at minimum one ofsaid plurality of signal generation means, for detecting a level of asignal output from said radio apparatus with respect to a correspondingsignal generation means, under control of said control means, whereinsaid control means determines a correction value for said transmissionweight in accordance with a detected result of said detection means. 7.The calibration system according to claim 5, wherein said signalconversion means comprises A/D conversion means for sampling a signalfrom said plurality of antennas at a first frequency, and down samplingmeans for sampling at a second frequency lower than said first frequencysaid signal sampled at the first frequency, wherein said down samplingmeans modifies a sampling timing at said second frequency in accordancewith said timing adjust signal.
 8. The calibration system according toclaim 5, wherein said signal conversion means comprises A/D conversionmeans for sampling a signal from said plurality of antennas at a firstfrequency, and means for adjusting a phase of an internal clock definingthe sampling timing at said first frequency by said A/D conversion meansin accordance with said timing adjust signal.
 9. A calibration method oftransmission directivity at a radio apparatus that carries out signalreception by adaptive array processing using a plurality of antennas,comprising the steps of: generating respective plurality of test signalsto be applied to said radio apparatus, sampling a signal from theplurality of antennas for conversion into a digital signal from ananalog signal at said radio apparatus, modifying a sampling timing atsaid signal conversion step in accordance with a timing adjust signal,calculating a reception weight to extract a desired signal based on saidsignal-converted signal to output match information that provides anindication of a desired reception directivity being achieved,determining a level of said timing adjust signal by which the desiredreception directivity is achieved based on the correspondingrelationship between said timing adjust signal and said matchinformation, obtained by sequentially modifying a level of said timingadjust signal, calculating a transmission weight to form a pattern of adesired transmission directivity at said determined level of a timingadjust signal, detecting a level of a signal output from said radioapparatus corresponding to said transmission weight, and determining acorrection value for said transmission weight in accordance with adetected result of said signal level.
 10. The calibration methodaccording to claim 9, wherein said signal conversion step includes thesteps of sampling a signal from said plurality of antennas at a firstfrequency, sampling at a second frequency lower than said firstfrequency said signal sampled at the first frequency, and modifying asampling timing at said second frequency in accordance with said timingadjust signal.
 11. The calibration method according to claim 9, whereinsaid signal conversion step includes the steps of sampling a signal fromsaid plurality of antennas at a first frequency, and adjusting a phaseof an internal clock defining a timing of said sampling at the firstfrequency in accordance with said timing adjust signal.
 12. Acalibration program of transmission directivity at a radio apparatusthat carries out signal reception by adaptive array processing using aplurality of antennas, causing a computer to execute the steps of:generating respective plurality of test signals to be applied to saidradio apparatus, sampling a signal from the plurality of antennas forconversion into a digital signal from an analog signal with respect tosaid radio apparatus, modifying a sampling timing of said signalconversion step in accordance with a timing adjust signal with respectto said radio apparatus, calculating a reception weight to extract adesired signal based on said signal-converted signal, and outputtingmatch information that provides an indication of a desired receptiondirectivity being achieved with respect to said radio apparatus,determining a level of said timing adjust signal by which the desiredreception directivity is achieved based on the correspondingrelationship between said timing adjust signal and said matchinformation, obtained by sequentially modifying the level of said timingadjust signal, calculating a transmission weight to form a pattern ofthe desired transmission directivity at said determined level of atiming adjust signal with respect to said radio apparatus, detecting alevel of a signal output from said radio device corresponding to saidtransmission weight, and determining a correction value for saidtransmission weight in accordance with a detected result of said signallevel.
 13. The calibration program according to claim 12, wherein saidsignal conversion step includes the steps of: sampling a signal fromsaid plurality of antennas at a first frequency, sampling at a secondfrequency lower than said first frequency said signal sampled at thefirst frequency, and modifying a sampling timing at the second frequencyin accordance with said timing adjust signal.
 14. The calibrationprogram according to claim 12, wherein said signal conversion stepincludes the steps of sampling a signal from said plurality of antennasat a first frequency, and adjusting a phase of an internal clockdefining the sampling timing at said first frequency in accordance withsaid timing adjust signal.